Fifteen years ago, police were making eight to 12 arrests at checkpoints, but those numbers have fallen steadily, traffic supervisor Sgt. Stephen Bresciano said Monday.

"We used to run out of manpower at checkpoints because everyone would have someone under arrest," Bresciano said.

The decrease in arrests reflects a wider trend. Nationwide, DUI arrests in 1995 totaled an estimated 1,436,000, according to the FBI. By 2013, the nation's population had climbed by about 50 million people, but DUI arrests had declined to 1,166,824.

A recent nationwide survey of drivers during weekend nighttime hours found the proportion of drivers who were at or above the blood-alcohol limit of .08 percent, the threshold for drunken driving, plummeted by 80 percent between 1973 and 2014, according to the National Highway Traffic Safety Administration.

Bresciano, a police officer for about 18 years, said reasons for the decline include stepped up enforcement, more public awareness and the plugging of loopholes in sanctions for convicted drunken drivers. He also mentioned a state law, effective July 1, that requires more offenders to install ignition interlocks. The devices require drivers to breathe into a meter, and a measurable amount of alcohol in the person's system disables the car.

Despite new technology and increased enforcement, however, alcohol-impaired drivers continue to cause havoc on the nation's roadways. About one-third of all crash deaths in the U.S. involve drunken drivers, and in 2013, 10,076 people were killed, the NHTSA reported.

Police are required to notify the media about scheduled checkpoints, but Bresciano said he could not gauge how many people avoid checkpoints after seeing notices in the newspaper or online. In neighboring South Windsor, police Lt. Scott Custer said the notifications likely have some effect, especially when spread through social media sites.

Custer said the downward trend in drunken driving, which South Windsor police also have seen, is laudable, but impaired driving is still a big public safety concern, and police have "just got to keep hammering at it."

Manchester police conduct four to six sobriety checkpoints each year, depending on how much state and federal grant money is available, Bresciano said. Another checkpoint is set for Friday night and early Saturday on West Middle Turnpike at the I-84 overpass.